In the 1980s, the Internet Engineering Task Force (IETF) released RFC 791 – Internet Protocol, which marks the standardization of IPv4. In the following decades, IPv4 has become one of the most popular protocols. Numerous people have developed various applications based on IPv4 and made various supplements and enhancements to IPv4, enabling the Internet to flourish. However, with the expansion of the Internet and the development of new technologies such as 5G and Internet of Things (IoT), IPv4 faces more and more challenges. It is imperative to replace IPv4 with IPv6. This course describes the reasons for IPv4-to-IPv6 transition and basic IPv6 knowledge.